The present invention relates to wireless communications in general and, in particular, to a satellite communications network.
In some communication systems, such as satellite communications systems, a base station or hub communicates on a shared forward channel to a number of user terminals. It is often advantageous to use a single, high rate signal on this forward channel instead of a number of low-rate channels to distribute information to all the users. In this manner, the information to the different users may be multiplexed in time.
If the users have different C/N (carrier to noise) characteristics, then the messages to some users may need to be at a lower rate than the rate at which other users can successfully receive. This has been handled in the art by keeping a constant symbol rate but varying the modulation and/or coding on a user by user basis based on the capabilities of the current user. The data messages are supplemented by physical layer headers that identify the modulation and coding. These headers are designed to be successfully demodulated by even the most disadvantaged user.
In order to extend the dynamic range of for a satellite communication, such as a DVB-S2 system to 30 dB, merely by way of example, expanding the header may be prohibitive. The length of the header may approach the length of the data block for advantaged users, yielding a highly inefficient system.
There is thus a need for efficient control signaling systems, methods, and apparatuses that apply to shared communication channels with wide dynamic range.
Furthermore, in some satellite communications systems, user terminals are mobile on platforms such as airplanes, trains, automobiles, etc. This mobility creates a number of problems for the system designer, such as wide dynamic range of signal quality, signal fading, blockages, etc.
There is thus a need for methods, systems, and apparatus that provide wide dynamic range solutions to mitigate the effects of blockage and fading of a mobile satellite channel.